Mandrel for driving pile shells



Oct. 22, 1963 c. B. HOPPE 3,107,497

MANDREL FOR DRIVING PILE sHELLs Filed Dec. 9, 1960 2 Shets-Sheet 1y CLEMENS B. HOPPE mff ATTORNEY Fl c 6 /f i 2 4 .l

.la IS l alla /f l OQ 6 KEI M FI G C. B. HOPPE MANDREL FOR DRIVING PILE SHELLS Oct. 22, `1963 2 Sheets-Sheet 2 Filed Dec. 9, 1960 INVENTOR. CLEMENS B. HOPPE Byma'a, ATTORNEYS rates This invention relates to apparatus for driving metal casings, usually called shells, into the earth for receiving concrete to fonm concrete piles, and contemplates an irnproved expansible and collapsible mandrel for driving corrugated shells.

The invention particularly is concerned with mandrels of the ftype having an inner mandrel part or member surrounded by an outer mandrel member comprising a plurality of longitudinally segmented exterior leaves which can be expanded and contracted by the inner mandrel member.

One feature of the mandrel of the invention is that it has a plurality of transversely-extending rod segments secured to the outside of the leaves and disposed in spaced relation with respect to the longitudinal axis of the mandrel. These rod segments have utility when used in driving shells having corrugations in that the rods, being arranged to extend across the corrugations at small acute angles, become partially embedded in the corrugati'ons of the shell when the leaves are expanded in the driving of the shell to provide a good driving engagement between the mandrel and the shell. When the mandrel is used in driving shells or casings having helical corrugations, the rods are attached to the leaves substantially at right angles to the longitudinal axis of the mandrel so that the rods of the mandrel and corrugations of the shell do not coincide with one another but rather lie at an angle to one another. This assures that the rods will bite into portions otf the corrugations when the ou-ter mandrel member leaves are expanded and form a good driving engagement between the mandrel and the casing shell. This arrangement not only overcomes the tendency of the mandrel to move relative to the shell and tear the corrugations causing expensive delays, but also facilitates driving shells under severe conditions. It also compensates for variations in the shell.

Another feature of the present mandrel is that the driving head is mounted `on the driving head stem by a universal ball and socket arrangement forming a universal joint. To this end, the upper pontion of the stem terminates in a hemispherical or ball portion which movably engages or rests in a hemispherical socket centered at the bottom of the driving head. Prior driving heads, in being integrally mounted on :the driving head stem, frequently fail by a shearing of the stem immediately underlying the head. By mounting the driving head movably on the stem, failures of the stem during the driving operation are minimized, if not entirely eliminated. In addition, this mounting permits 4the driving head to rock with respect to the stem to adjust itself on the outer mandrel member leaves to rest equally on all leaves, thereby transmitting the driving force directly and equally from the head to all the leaves and thereby to the shell without alfecting the head stem.

arent it The present mandrel also includes a driving shoe for l.

engaging the bottom of the shell during the driving operation, the shoe being attached to a cross-bolt or pin passing through the hollow inner mandrel member by a wire rope or cable. Prior driving shoes have been attached to such a bolt or pin by a steel strap. In practice, this strap, being free to vibrate during driving, frequently failed by shearing at the driving shoe. By attaching the shoe to the inner mandrel member with a liexible member, such as wire rope or chains, which is not subject to having vi- 3,107,497 Patented Oct. 22, 17963 ice 2 brations set up in it during the driving operation; these failures are minimized, if not entirely eliminated.

The invention is applicable generally to mandrels having expansible and collapsible segments or leaves, and for the purpose of illustration will be described in connection with a mandrel embodying features of the mandrel of my copending application Serial No. 642,418, iiled February 26, I1957, now Patent No. 2,977,770, of which this application is a continuation-impart.

The invention will be further described in connection with the accompanying drawings, in which FIG. 1 is a vertical sectional view, partly in elevation, of a mand-rel embodying the invention and shown in its fully contracted or collapsed position;

FIG. 2 is a vertical sectional view similar to FIG. l, but showing the mandrel in its fully expanded position;

FIG. 3 is an enlanged cross-sectional view, taken on Iline 3--3` of FIG. 1, showing the mandrel in its collapsed position;

FIG. 4 is a View similar to FIG. 3, but taken on line 4-4 of FIG. 2, showing the mandrel in its fully expanded position;

FIG. 5 is an enlarged vertical sectional view, partly in elevation, of a portion of the mandrel in its fully expanded position showing the rods securely engaging the shell; and

FIG. r6 is a vertical sectional view similar to FIG. l, but showing the mandrel in an intermediate position.

The improved mandrel of the invention comprises an inner mandrel member 1 and an outer mandrel member 2. The inner mandrel member is a continuous tube. The outer mandrel member comprises .three arcuate sections or leaves 3, 4 and 5 which in the expanded position yform a circular yassemblage that ilts inside the pile shell casing S, as shown in FIG. 4. A driving stem 6 is slidably received in the upper portion of the inner mandrei member. The stem terminates at its upper end in a machined hemispherical or ball portion 7. A driving head 8, which receives the driving blows of the hammer, has a machined hemispherical socket 9 which receives the ball portion 7, form-ing a ball-and-socket or universal joint. This join-t provides sullicient freedom of movement between head 8 and s-tem 6 to allow the head to swivel on the driving stem and to adjust itself during the driving operation to rest equally on the upper ends of all of the outer mandrel member leaves, thereby equalizing fthe driving force imparted to the leaves. A cover plate 11 extends over the opening in the driving head in which the .ball portion 7 is received. This plate protects the universal joint from Aforeign matter and from damage during the driving operations. The cover plate may be secured to the driving head in any manner, as for example, 'by a circumferential weld.

The inner mandrel member 1 has upper and lower bosses 12 and 13` ywhich have ydownwardly and inwardly sloping wedge surfaces 14 and 16, respectively, which cooperate with upper and lower wedge segments 17 and 18 on the inner surfaces of the leaves 3, 4 and 5 of the outer mandrel member and have inwardly and downwardly sloping surfaces 20 and 21, respectively. Any suitable number of such bosses and wedge segments may be provided at longitudinally spaced intervals on the inner mandrel member and rthe outer mandrel member leaves. At the beginning of a driving operation, the wedge sur-faces 14 and 16 bear against sloping surfaces -20 and 21, respectively, to expand the leaves to bring 'the inner mandrel member is enlarged to provide a wedge segment 23 having :an upwardly and outwardly extending wedge surface 24. Cam brackets 26, extending lfrom the inner surface of the leaves, project through the slots 22 and have a Wedge surface 27 engaging the corresponding wedge ysurface 24 of the inner mandrel member. When the inner mandrel member is raised, the wedge surfaces 24 bear against and exert a wedging action on cooperating wedge surfaces 27 carried on cam brackets 26. This wedrging action `forces the cam brackets and their attached leaves inwardly to bring the leaves to their collapsed position, Ialso shown in lFIG. 1. The cam brackets 26 extend downwardly inside the hollow inner .mandrel member a distance such that when the mandrel is inserted in the pile shell and the inner mandrel member is moved to extend the leaves outwardly the maximum distance, the free or distal ends of the cam brackets still lie below the lower ends of the slots and opposite a portion of the wall of the inner mandrel member, so that the leaves are held to the inner mandrel member.

To facilitate the collapsing of the leaves `of the outer mandrel member after a driving operation, ashereinafter more fully described, and to connect the driving stem to the inner and outer mandrel members, the upper portion of the inner mandrel member 1 has three longitudinallyextending slots 28 staggered longitudinally and circumferentially, one opposite each leaf. The leaves of the outer mandrel member each have a slot 29 opposite one of slots 28. A floating cam lever 31 is positioned in each set of the slots. The outer part of each cam lever projects through the elongated, longitudinally-extending slot 29 in the adjacent leaf of the outer mandrel member. The intermediate portion of each cam lever lies in the slot 28 in the inner mandrel member. The inner part of each cam lever projects into an opening or slot 32 in the driving stern 6. The cam levers 31 are referred to as floating since they are not mounted on pintles but are free to move, to a limited extent, relaftive to the stern `6, the inner mandrel member, and the leaves of the outer mandrel member.

The upper portion of the mandrel is provided with a loose fitting collar 33 which is suspended from hammer cables C. This collar is the means by which the mandrel is manipulated into and out of the shell. Since the collar hangs loose during the driving operation, the mandrel is free to rotate with the shell, which tends to turn or to be threaded into the earth, due to its helical corrugations, without twisting the cables which support the collar.

The inside diameter of the collar is only slightly greater than the outside diameter of the outer mandrel member when the leaves are in their expanded position. Thus, the collar lies sufficiently close to the outer edges of the cam levers 31 to prevent them from falling out of the slots 28, 29 and 32 in which they are mounted. This eliminates the necessity of pintles for mounting the cams, which is desirable since the pintles tend to shear under the forces to which they lare subjected.

At intervals spaced in the longitudinal direction of the mandrel axis a plurality of integral, elongated, rigid, rod-like projections 34 are attached, las by welding, to the exterior surfaces of the leaves 3, 4 and 5 of the outer mandrel member. These rod-like projections may be of any suitable cross-sectional shape, such as round or half-round, and may be spaced a distance corresponding to the distance between adjacent corrugations of the shells. When shells having helical corrugations are to be driven, such as illustrated in the drawings, the projections are arranged at approximately right angles to the longitudinal axis of the mandrel. As thus arranged, the projections are disposed at an acute angle with respect to the corrugations. Therefore, when they are in engagement with the shell, they extend across the corrugations thereof. -lt is to be understood that when the corrugations `of the shell are not helical, as for example, at

right angles to the longitudinal axis of the shell, the projections are then so angularly attached to the leaves that they form acute angles with respect to the corrugations. When the leaves of the outer mandrel member are moved outwardly under the expansive force exerted by the inner mandrel member, these projections become partially embedded in the corrugations and form a sccure driving engagement.

When the mandrel is fully inserted in the shell, its lower end will engage the closed lower end 36 of the shell. As shown in FIG. 1, the lower end of the inner mandrel member 1 .terminates in an outwardly-extending boss 37 having a downwardly and inwardly sloping wedge surface 38. This wedge surface cooperates with downwardly and inwardly sloping surfaces 41 of wedge segments 42 extending inwardly at the lower end portion of each of the leaves of the outer mandrel member. The wedge surface 3S cooperates with the wedge surfaces 41 to force the leaves of the outer mandrel member outwardly, similar to the manner in which Wedge surfaces 14 and 16 of bosses 1'2 and -13 cooperate with surfaces 20 and 21 of wedge segments 17 and '18.

A pin or bolt 43 extends crosswise of the inner mandrel member a short distance above the boss 37. A wire rope 44 is looped to form an eye surrounding pin 43. Both ends of the wire rope pass through the lower open end of the outer mandrel member and are secured to a driving shoe 46 which engages the bottom of the casing during a driving operation. The ends of the wire rope are secured to the driving shoe by passing them through a central opening or bore 47 in the driving shoe and anchoring them in an outwardly-flaring lower portion of the opening as by a filling of weld or solder metal or otherwise, as indicated at 48. Since the wire rope attaching the driving shoe to the mandrel is flexible, the driving blows applied to the mandrel will not set up vibrations in it causing eventual failure of the attachment. ln order to keep wire rope 44 from entangling itself, and in order to positively guide the wire rope into the hollow center of inner mandrel member 1, a guide sleeve 49 surrounds the wire rope.

FIG. 1 shows the improved mandrel of the invention suspended inside a `cylindrical corrugated metal shell casing S of a type widely used for driving into the earth to form concrete piles. The head 8 is shown in its elevated position prior to driving the mandrel. In this position, the outer end of each of the cam levers 31 is in the upper part of the slot 29 of its corresponding outer leaf of the outer mandrel member and the inner end is in bearing contact with the stem 6 where it enters the slot 32 therein. The wedge surfaces 14 and 16 of the inner mandrel member are above and out of contact with the corresponding outer mandrel member surfaces 20 and 21. However, the upper portion of the wedge surfaces 27 of the cam brackets 26 of the outer mandrel member leaves are in Abearing contact with the surfaces 24 of the wedge segments 23 of the inner mandrel member and the leaves of the outer mandrel member are accordingly held in their inner or collapsed positions. When the mandrel has been lowered into casing shell S by the hammer cables C far enough to cause driving shoe 46 tto engage the closed lower end 36, the driving shoe 46 will be held against further longitudinal movement within the shell. When the mandrel is lowered vfarther into casing shell S, the bottom of the leaves forming outer mandrel member 2 will engage the driving shoe and will also be held against further longitudinal movement. As the inner mandrel member is lowered still farther into the shell, the leaves of outer mandrel member 2 will be wedged outwardly to engage shell S =by the wedging action of wedge surfaces 14, 16 and 38 on wedge segments 17, 18 and 42. Simultaneously, the wedge surfaces 27 of the cam brackets 26 will slide upwardly along the wedge surfaces 24 of the wedge segments 23 as the leaves of the outer mandrel member are forced outwardly. The first few driving blows delivered to driving head 8 will be transmitted from the bottom of the head to the top of the inner mandrel member causing wedge surfaces 14, 16 and 38 to wedge segments 1.7, 1S and 42 of the leaves outwardly still more, forcing the leaves to the fully expanded position shown in PXC?. 2 and into close contact with the casing shell S. When the leaves have been fully expanded in the shell, the top of the inner mandrel vmember l-ies in the same horizontal plane as the tops of the outer mandrel member leaves. ln this position, the driving head 8 bears on the top of all the leaves and the top of the inner mandrel member while the rod-like projections 34 are forced against the corrugations of the shell by the wedging `action of the inner mandrel member wedging surfaces 14, 16 and 38 on the outer mandrel member wedging surfaces 20, 21 land 41 during driving, as shown in FIGS. 2 and 5, and by reason of their angular relation to the corrugations, and bite into or become partially embedded in those portions of the corrugations with which they make ydirect contact, thereby providing a -good driving connection between the mandrel and the casing shell. Since the project-ions are spaced laterally and longitudinally about the mandrel and engage portions of the corrugations of the shell throughout its length and circumference, the force of the driving blows is transmitted to the shell in a relatively uniform fashion throughout its length and circumference. This means that a minimum of strain will be exerted on any one part of the shell thereby insuring, insofar as is possible, that the shell Iwill not tear but remain in one piece during the driving operation. During the driving operation shoe 46 will be :held against and reinforce the bottom 36 of the shell by the bottom of the leaves of the outer mandrel member.

When the shell has been completely driven, and the mandrel is to be removed, an upward pull is applied by the hammer cables C on Ithe collar 33 and by the collar on the driving head 8. In the initial upward movement of the driving head, cam levers 31 :come into action in collapsing the leaves of the outer mandrel member. ln this 4initial faction, the cam levers perform three important functions, namely, -their outer ends hold the leaves of the outer mandrel member down, their intermediate portions engage the tops of the slots 28, raising the inner mandrel member and breaking lthe contact of the leaves of the outer mandrel member with the inner mandrel member which were bound Iby the force of the pile hammer, and their inner ends lock the stern 6 of the driving head to the inner mandrel member. That is, as the inner mandrel member is pulled slightly upwardly, the inner end `of each cam lever engages the bottom of slot 32 while the intermediate portion of the upper sur-face of the cam lever contacts the upper portion of the slot 28 of the inner mandrel member. As the stem 6 is further withdrawn, the outer end of each lever bears down on the lower end of the leaf slots 29, while the intermediate portion of the upper surface of the cam lever bears on the upper portion of the slot 28 of the inner mandrel member and lifts it sufficiently to break the contact between the inclined surfaces o-f the leaves of the louter mandrel member and the inner mandrel member. As stem 6 is further withdrawn, the `cam levers lock against the inner mandrel rmember 11 and stop the sliding action of the stern therein. As the inner mandrel member continues to move upwardly, the surfaces 14 and 16 move out of contact with the surfaces 20 and 2.1, as shown in FIG. 1, and the surfaces 24 move upwardly above the surfaces Z7 of the brackets 26 to pull the leaves inwardly to the position shown in FIG. 1, thereby freeing the mandrel from engagement with the shell and permitting the mandrel to be removed by further upward pull on cables C.

Various changes may be made in the details of construction of the mandrel herein described without departing from the invention or sacrificing any of the advantages thereof, the scope of the invention being set forth in the appended claims.

l claim:

1. A mandrel for driving pile shells comprising an inner mandrel member and an outer mandrel member including a plurality of expansible and collapsible rigid leaves, the inner mandrel member being hollow at least at its lower end, a pin extending transversely through said hollow lower end of the inner mandrel, a driving shoe, a wire rope having a looped portion passing around said pin and having its ends attached to said shoe, and a rigid guide sleeve surrounding said rope between said shoe and said looped portion of the rope.

2. ln combination with a pile shell having circumferentially extending corrugations, a mandrel for driving said pile shell, said mandrel having a plurality of expansible and collapsible rigid leaves extending in the longitudinal direction thereof, an inner mandrel member for expanding and collapsing the leaves, each leaf having a plurality of integral, elongated, rigid, rod-like projections extending outwardly from its exterior surface and extending circumferentially thereof, said projections being relatively long, of relatively small cross-secional area and disposed at an acute angle `with respect to the corrugations of the pile shell, the projections extending crosswise of the corrugations of the pile shell at an acute angle and being partially embedded in said corrugations.

3. The combination set forth in claim 2 in which the mandrel includes a driving head, a driving stem, and a universal joint connecting said head to said stern. l

References Cited in the le of this patent UNITED STATES PATENTS 

1. A MANDREL FOR DRIVING PILE SHELLS COMPRISING AN INNER MANDREL MEMBER AND AN OUTER MANDREL MEMBER INCLUDING A PLURALITY OF EXPANSIBLE AND COLLAPSIBLE RIGID LEAVES, THE INNER MANDREL MEMBER BEING HOLLOW AT LEAST AT ITS LOWER END, A PIN EXTENDING TRANSVERSELY THROUGH SAID HOLLOW LOWER END OF THE INNER MANDREL, A DRIVING SHOE, A WIRE ROPE HAVING A LOOPED PORTION PASSING AROUND SAID PIN AND HAVING ITS ENDS ATTACHED TO SAID SHOE, AND 